The synthesis and characterization of a THF pendant, dimeric Mo cyclopentadienyl complex is reported and the structure characterized by NMR, FTIR, and UV-vis spectroscopies. The dimer was found to undergo metal-metal bond homolysis under either photochemical or electrochemical conditions to yield an odd-electron complex. Cyclic voltammetry under varying scan rate conditions from 25 to 10 000 mV/s demonstrates a dynamic equilibrium process that we assign to the formation of either an intramolecular 19-electron (18 + delta) complex or a bare 17-electron complex. Photolysis of the dimer in room temperature solution could be monitored as a loss of the d pi-d sigma* transition at 503 nm by transient absorption spectroscopy. The recovery of the transient absorption signal at 410 nm follows first-order kinetics at a rate of 5 x 10(3) s(-1).